Boundaries of towns and other minor civil divisions, and in some cases of counties were ill defined, so enumerators were frequently uncertain whether a family resided in their own or an adjoining district. For this reason, it is not unusual to find individuals and families listed twice in the census and others missed entirely."
And again:
In a few states and territories, such as Arizona, Louisiana, Orleans, South Carolina, and others, the county divisions have been known by other names. In other places in some years, counties have not existed or have not been used, so other means of dividing up the state or territory have been used. Common examples of these names are Beat, Division, Judicial District, District, etc.
The supervisor of census is by law charged with the following duties:First. To propose to the Superintendent of the Census the apportionment of his district into subdivisions most convenient for the purpose of enumeration. These subdivisions are not allowed by law to exceed 4,000 inhabitants, according to the census of 1870, and can be made as much smaller as the good of the service may require. Administratively, the census office has favored the plan of small subdivisions; and of the 15,000 subdivisions reported up to the present date, the average estimate of population is not in excess of 2,000. Generally speaking, each existing civil division, whether a town, township, military district, "beat," or precinct, has been constituted one or more enumeration districts. In comparatively few cases two townships or more, of small population, have been constituted one enumeration district. It is anticipated that the total number of enumeration districts for all the States and Territories will be closely in the neighborhood of 28,000.
